Mike Walter wrote:
Ah, but you do have C.A. documentation online at the CA SupportConnect
site. :-)
Defragging and resizing disks are two different goals. In
de-fragmenting, you are trying to move free space between minidisks
into larger free space sizes by moving MDISKs around. The "COMPRESS"
command will do so, for specified subpools, but only de-fragging free
space within the same subpool on the same volume.
Re-sizing **CMS** MDISKs is done with the CHGMDISK subcommand. You
can reduce the MDISK size (provided you don't try to make it smaller
than needed for the number of blocks currently allocated) and even
change the blksize, etc. That's a different goal than moving MDISKs
around to consolidate free space into larger chunks.
Not sure on the DFSMS vs DDR question for VM:Secure and VM:Direct
since my earlier testing of DFSMS disk moving didn't save very much
time over DDR (surprised me), and changing MDISK sizes with DFSMS (vs
alloc new MDISK, format, copyfile) didn't seem to make all that much
difference either. Maybe because we run with a modification to DMSFMT
(?) which eliminates the block readback after the block format (saves
50% of the formatting time). But newer DASD architecture even seems
to make that mod nearly useless, too. Nonetheless, I *believe* that I
recall VM:Secure and VM:Direct supporting DFSMS as an easily changed
option. That's probably what spurred me to run performance tests of
the differences some years ago. A little searching of this list may
turn up my posts showing the differences.
Mike Walter
Hewitt Associates
The opinions expressed herein are my, not those of my employer.
*"Richard Schuh" <[EMAIL PROTECTED]>*
Sent by: "VM/ESA and z/VM Discussions" <[email protected]>
12/24/2005 06:36 PM
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Re: Minidisk defragger?
Rich Greenberg wrote:
>On: Sat, Dec 24, 2005 at 04:13:43PM -0600,Mike Walter Wrote:
>
>} VMSECURE COMPRESS (and assumedly VMDIRECT COMPRESS) uses DDR under the
>} covers. Thus, any minidisk.
>
>Thanks Mike. Thats a VMS function I never used. So you can do Linux
>disks, just can't resize a CMS disk.
>
>
>
I don't have the CA documentation at home, so I don't know the answer to
this. Can you tell VM:Secure/VM:Director to use DFSMS instead of DDR?
That was/is an option in Dirmaint. If so, you can resize CMS disks and,
possibly, any disk that is preformatted with one block size.
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Back in the days of converting from 3380 to 3390, DFSMS was the only
choice. It was also a very fast formatter when copying from a smaller to
a larger disk. In fact, it so far outperformed FORMAT that we use it to
copy a 1 cylinder disk to any size disk in place of using format. Well,
not just any size. If formatting a disk larger than about 2770 cylinders
(memory is a little fuzzy, so the size is not exact), DFSMS failed with
no error indication. I wouldn't really expect it to beat DDR in a
straight disk image copy. Almost any copy program that is worth its
salt knows about cache and FTR/FTW.
What are you doing messing around the computer at this time (midnight
CST for those who don't know that Mike is in King Richard's realm -
Richard Daly, Chicago).
